Silver Plating

Silver plating is simply the method of depositing a thin layer of silver onto a conductive surface. The surface normally consists of a conductive metal base which allows a current to be passed through it to form a complete circuit. This allows the silver particles in the electrolyte solution to bond with the item being silver plated, the item being electroplated is also referred to as the cathode.
When plating silver, it is a white colored semi-precious metal. Due to its property of high electrical conductivity it is often used in the electronics and semiconductor industries. Due to silver’s conductivity, the microwave and satellite industries use it to carry high frequency signals and reduce the amount of heat generated compared with copper. Another benefit is the reduction in “skin depth” generated when using silver compared to other less conductive materials.
Silver is also the best heat conductor of all metal plating materials, and offers great solderability. Unlike copper, oxidized silver retains a conductive surface. Copper oxide builds resistance that is much higher than silver oxide.
Silver’s lubricity and high temperature resistance allow engine manufacturers to use silver in the place of lubricants. It is used on bearing surfaces and anti-galling applications. Some applications might be bearings or gear teeth that are exposed to high temperatures in jet engines, or auxiliary power units where lubricants fail.
Hardness varies from about 90 Brinnell to 135 Brinnell hardness numbers depending on process and plating conditions. Solderability is excellent, but decreases with age. Plating silver offers the best electrical conductivity, though this conductivity diminishes with time and oxidation.
Silver acts as an economically beneficial metal plating that may be put to good use for a lower price compared to other precious metals like gold or platinum.

Coastline Metal Finishing has two types of silver plating available :

Matte silver plating : is used in areas requiring low electrical resistance and good solderability
Semi bright silver plating : is used where low electrical resistance isn’t a primary requirement and in some areas where a decorative finish is desired. Semi bright silver is more resistant to fingerprinting during assembly operations than matte silver and it has good solderability Properties

Silver gives excellent anti-fretting properties as well as providing a corrosion resistant surface. It also has high electrical conductivity, and is FDA compliant (previously ‘FDA approved’) for applications in the food and medical industries.

Classification For The Thickness of Silver Plating Relating to The Solutions

  • The minimum thickness for silver plating is equal to 0.5 microns. This is used mainly for a decorative finish on items with minimal handling.
  • Heavy silver plate is classed as 2.5+ microns. The normal thickness we apply would be between 2.5 – 6 microns dependent upon the item and its intended use. This provides a long lasting finish on high wear items such as; watches, buckles, trophies and jewellery.

Highest Electrical & Heat Conductivity

Silver has the highest electrical conductivity, heat conductivity and the lowest contact resistance of any metal making it ideal for the electronics industry. It is often chosen as a less-expensive alternative to gold for electrical connections

Toxic To Bacteria & Other Micro-Organisms

Silver has found extensive use in the communication and medical industries. Silver is toxic to many bacteria and other micro-organisms. It is used in many home water filtration systems.

About Silver Plating Baths

The majority of all silver plating is performed using an alkaline cyanide solution. Silver Plating baths can be modified so that the silver deposit ranges from matte to bright as deposited. Unless appearance is an issue, matte silver deposits are preferred. They are less brittle and solder better than do bright deposits. As with any plating bath, great care has to be taken in controlling all parameters.

About Silver Tarnish & Silver Sulfide

Silver tarnish is not an oxide; silver oxide does not form easily. When silver reacts with hydrogen sulfide, silver sulfide (tarnish) is produced. Silver Sulfide is not conductive nor solderable. Often a secondary treatment is applied after plating which inhibits the formation of Silver Sulfide, allowing for easier soldering of the part.

Silver Plating Specifications

Hi-Tech Plating offers all types of plated silver per specifications QQ-S-365 and ASTM-B-700-97.
Corrosion Resistancesilver plate is resistant to many organic acids, as well as sodium and potassium hydroxide. When sulphur is a hazard, special anti-tarnishing treatments can be applied to greatly increase the protection. Silver is not recommended for use with inorganic acids; nitric, hydrochloric, sulphuric, etc.

Anti-galling and Anti-fretting

Silver has a low coefficient of friction, making it ideal as an anti-galling (cross-transfer of metal, and subsequent adhesion and seizure). Stainless steel bolts and screw threads, and parts made in titanium, can all be protected

Material pair Friction coefficient
Stainless vs stainless 0.80
Titanium vs titanium 1.00
Hardened steel vs itself 0.35
Cadmium plate vs steel 0.20
Silver vs stainless or Ti 0.18

Because of its oxidation resistance, silver plate is ideal in fretting situations (splines, couplings, housings), where oxidation, and abrasion by the oxide debris is eliminated.